I love both names but I think Oliver and Oscar are a little close. They both start with an "O" and end in a "R". Plus your son Miles might feel left out, especially since your dog even has an 'O' name.

Quincy - Nice name and I think it goes good in your sibset.Hugo - This is my favorite as long as Miles it never called Milo. Oliver, Miles, and Hugo are a very cool set of names.Sebastian - I wouldn't use this if it causes problems with your last name.Leo - I think Leo and Theo could get confusing.

Thanks for the confirmation! Oscar is officially off the list.
I really appreciate all of the other feedback as well. You all seem to know exaclty the names I like and I have literally considered each of the suggested names but they have either been rejected by DH or they are way too rhymey with our last name. If it helps at all, last name is Rothman, so while I agree that Quentin is more "name-like" than Quincy, I just think it doesn't work with Rothman. Same for so many of the other suggested names that end in "n" (Dorian, Nolan, Julian). I like the suggestions Malcolm and Graham, but I have an older cousin Malcolm that has ruined the name for me, and DH is Bram so Graham is out. Other suggestions I love: Isaac, Elias, Levi, Felix, and Elliott have all been rejected by DH. Sigh.
It looks like for now we are down to Quincy and Hugo, possibly Leo. Maybe we'll just wait to meet him and decide. Thanks again!

Hugo definitly. My fave boy name! I think the two oscar and oliver are too close. Suggestions not mentioned dexter, angus, jasper and zac. (Hugo, sebastian, felix and leo were also on my list with the ones i just suggested.so we have similar taste)!